The use of acoustic transducers in fatigue testing is well known. Typically, one or more piezo-electric acoustic transducers are attached to a test surface of an item subjected to such fatigue testing. The acoustic transducers provide test data regarding the acoustic energy emissions of the instrumented test surface.
However, it is not uncommon for acoustic transducers to become completely detached from the test surface being monitored during fatigue testing. Such debonding of the acoustic transducer typically occurs slowly such that the transducer does not exhibit evidence of the failing bond until the signal provided by the transducer has degraded substantially. As a result, there is steady degradation of the acoustic transducer's adhesive bond and a consequent incremental loss of data quality prior to complete failure of the adhesive bond. It is also thought that such debonding or gradual failure of the adhesive bonding agent may introduce spurious transient or cracking signals, thereby rendering the data provided by the transducer unreliable.
Thus, one of the problems commonly associated with the use of such acoustic transducers during fatigue testing includes degradation and/or failure of the adhesive with which the piezo-electric transducers are attached to the test surface and the consequent inability of the failed adhesive to adequately transmit acoustic energy from the test surface to the acoustic transducer.
Additionally, a tradeoff exists between fatigue resistance and acoustic transmission capability in the use of the various coupling and adhesive bonding agents. Those materials which provide desirable acoustic coupling properties typically provide poor bonding properties and vice versa. Thus, those adhesives which are most likely to withstand the stress associated with fatigue testing do not transmit acoustic energy well. Conversely, gel couplants, which transmit acoustic energy well, do not provide a bond having sufficient strength to adhesively bond acoustic transducers in place during fatigue testing.
Thus, although gel couplants have desirable acoustic transmission properties, such gel couplants are not capable of mounting an acoustic transducer to a test surface, and conversely, various adhesives have the desired fatigue resistant properties, but lack the acoustic transmission ability of gel couplants. As such, according to contemporary methodology, the effectiveness of acoustic energy transmission is compromised by utilizing adhesive bonding agents having the required fatigue resistant qualities, but lacking the desired acoustic energy transmission properties.
As such, although the use of such fatigue resistant adhesive bonding agents has proven generally suitable for the mounting of acoustic transducers, the use of such fatigue resistant bonding agents possesses inherent deficiencies which detract from their overall performance and desirability. In view of the shortcomings of the prior art, it is desirable to provide a means whereby acoustic transducers are mounted to a test surface in a manner which does not subject them to the undesirable effects of fatigue and which also provides the desired acoustic transmission of gel couplants.